1. Technical Field
The present invention relates to a method of estimating a channel, and more particularly, to an apparatus and a method of estimating a channel in consideration of a residual synchronization offset in which a phase generated by the residual synchronization offset in proportion to a difference between a channel estimation time and a channel compensation time is reflected in a channel estimated value in the case in which an orthogonal frequency division multiplexing (OFDM) symbol estimating the channel and an OFDM symbol compensating for the channel are different from each other.
2. Description of the Related Art
In an orthogonal frequency division multiplexing (OFDM) transmission scheme, which is one of schemes of transmitting a plurality of carriers in which several carriers are used, input data are carried on a plurality of sub-carriers having orthogonality and are transmitted in parallel with each other.
In the OFDM transmission scheme, a transmission period in each channel is increased by the number of carriers. In this case, frequency selective channel characteristics appearing by using a wide band at the time of transmitting high speed data are approximated to frequency non-selective channel characteristics by a narrowed channel. Therefore, in the OFDM transmission scheme, distortion by a channel may be compensated for by only an equalizer of a single sample simpler than a single carrier system, such that the OFDM transmission scheme has been widely used in a high speed data transmission system of several fields such as multimedia data transmission, and the like.
In a system using the OFDM transmission scheme, a channel is estimated using a pilot sub-carrier. As a scheme of estimating a channel using a pilot sub-carrier, there are several schemes such as a linear minimum mean square error (LMMSE) scheme, which is a scheme of estimating a channel using statistical characteristics of the channel, a maximum likelihood (ML) scheme, which is a scheme of calculating an estimated value having a maximum likelihood value, a general linear and polynomial interpolation scheme, and the like.
The channel is estimated by one of these several schemes of estimating a channel and is then compensated for based on the estimated channel value.
However, in a scheme of estimating a channel according to the related art, an influence of a difference between an OFDM symbol estimating the channel and an OFDM symbol compensating for the channel and a residual synchronization offset generated by the difference is not considered in estimating the channel and compensating for the channel. That is, in the case in which the OFDM symbol estimating the channel and an OFDM symbol compensating for the channel are different from each other, channel estimating performance is deteriorated due to the residual synchronization offset.